The cerebrum contains regions that process different sensations and perceptions. The central sulcus separates the motor and sensory areas. Sensations are the arrival of information from senses, while perceptions are conscious awareness of sensations. The cerebrum contains areas that process general senses like temperature, pain, and touch, as well as special senses like vision, smell, and hearing. Sensory information travels from receptors through three neurons to reach awareness in the thalamus and cerebral cortex.

1. Week 11: Brain: functions of the cerebrum
General Senses; Motor and sensory relays to & from
brain
Eye and vision
****REVIEW SESSION???
Lab 10: special senses - eye and ear; tactile receptors;
reflexes
Today- Quiz on Lab 9
Lecture Reading: Martini: pp 466-477, 536-545, 424-428, 495514, 555-574
Lab Reading: Martini: pp 555-563, 574-588, 499-501, 436-43
AM: 88-89,93,104-6

2. Regions and Functions of the Cerebral Cortex
Central sulcus separates motor and sensory areas
Figure 14–15a

3. Sensation
• The arriving information from senses
Perception
• Conscious awareness of a sensation

4. General Senses
• Describe our
sensitivity to:
– temperature
– pain
– touch
– pressure
– vibration
– proprioception
Special Senses
•
•
•
•
•
Olfaction (smell)
Vision (sight)
Gustation (taste)
Equilibrium (balance)
Hearing

5. Receptive Field
• Area monitored by a single receptor cell
• The larger the receptive field, the more difficult to
localize a stimulus
Figure 15–2

6. Classification Of Sensory Receptors
• Defined by the nature of the stimulus that
excites them:
– nociceptors (pain)
– thermoreceptors (temperature)
– mechanoreceptors (physical distortion)
– chemoreceptors (chemical concentration)

7. Pain Receptors
• also called nociceptors
• common in:
– superficial skin
– joint capsules
– periostea of bones
– around the walls of blood vessels
• Free nerve endings with large receptive fields
• May be sensitive to:
– extremes of temperature
– mechanical damage
– dissolved chemicals, (eg., released by injured cells)
Figure 15–2

8. Myelinated Type A Fibers
• Carry sensations of fast pain, or prickling pain, such as
that caused by an injection or a deep cut
• Sensations often trigger somatic reflexes
• Relayed to the primary sensory cortex and receive
conscious attention

9. Type C Fibers
• Carry sensations of slow pain, or burning and
aching pain
• Cause a generalized activation of the reticular
formation and thalamus
• aware of the pain but only have a general idea of
the area affected

10. Thalamus
Reticular Formation

11. Thermoreceptors
• Also called temperature receptors
• Free nerve endings located in:
– the dermis
– skeletal muscles
– the liver
– the hypothalamus
• Sent to:
– the reticular formation
– the thalamus
– the primary sensory cortex (to a lesser extent)

12. Mechanoreceptors
• Sensitive to stimuli that distort cell membrane
• Contain mechanically regulated ion channels
whose gates open or close in response to:
– stretching
– compression
– twisting
– or other distortions of the membrane

13. 3 Classes of Mechanoreceptors
• Tactile receptors:
– sensations of touch, pressure, and vibration
• Baroreceptors:
– detect pressure changes in the walls of blood
vessels and parts of digestive, reproductive,
and urinary tracts
• Proprioceptors:
– monitor the positions of joints and muscles
– eg., muscle spindles

14. Fine Touch and Pressure Receptors
• extremely sensitive
• narrow receptive field
• provide detailed information about:
– exact location
– shape
– size
– texture
– movement
Crude Touch and Pressure Receptors
• have relatively large receptive fields
• provide poor localization and little info about
stimulus

15. Tactile Receptors
Figure 15–3

16. Tactile Receptors in the Skin
• Free nerve endings:
– sensitive to touch and pressure
– situated between epidermal cells
– tonic receptors with small receptive
fields
Tonic= always active
• Root hair plexus nerve endings:
– monitor distortions and movements
across the body surface
– adapt rapidly (will “turn off” after
stimulated), best at detecting initial
contact and subsequent movements
Figure 15–3a

17. Tactile Receptors in the Skin
• Merkel’s discs:
– fine touch and pressure receptors
– extremely sensitive; tonic
– very small receptive fields
• Meissner’s corpuscles :
– fine touch, pressure, and lowfrequency vibration
– Rapidly adapting
– abundant in the eyelids, lips,
fingertips, nipples, and external
genitalia
Figure 15–3c

18. Tactile Receptors in the Skin
• Pacinian corpuscles:
– sensitive to deep pressure
– rapidly-adapting
– sensitive to pulsing or highfrequency vibration
• Ruffini corpuscles:
– sensitive to pressure and distortion
of the skin
– Located in deep dermis
– tonic receptors; little if any
adaptation
Figure 15–3e

19. Chemoreceptors
• Respond to water-soluble and lipid-soluble
substances
• Located in carotid arteries and aorta
• Monitor Ph, carbon dioxide, and oxygen levels
in blood

20. Anatomy of the Spinal Cord
• Gray matter:
– neuron cell
bodies, neuroglia,
unmyelinated
axons
• White matter:
– ascending and
descending
axons
– columns of
axon bundles
with specific
functions
Figure 13–5b

21. Organization of White Matter
• 3 “white columns” (funiculi) on each side of
spinal cord:
– posterior
– anterior
– lateral

22. Organization of Sensory Pathways
Third-Order Neuron
Second-Order Neuron
First-Order Neuron

23. First-Order Neuron
• Sensory neuron
• Cell body located in dorsal root ganglion or
cranial nerve ganglion

24. Second-Order Neuron
• Sensory neuron synapses on an interneuron in
the CNS
• May be located in the spinal cord or brain stem
• Axon crosses!

25. Third-Order Neuron
• second-order neuron synapses
on a third-order neuron in the
thalamus
• Right thalamus and primary
cortex receive sensory
information from left side of
body and vice versa.
• “reaches our awareness”